Project Summary/Abstract Physical Sciences Inc. (PSI) is continuing the pursuit of new clinical applications and advanced multimodal capabilities for its novel retinal imaging technology based on an adaptive optics line-scanning ophthalmoscope (AO-LSO). The Compact Adaptive Optics Retinal Imager (CAORI) eliminates high-speed scanning components, reduces the clinical footprint compared to research adaptive optics scanning laser ophthalmoscopes (AOSLO), and simplifies AO optical design while preserving the confocal advantage. In the proposed Phase II program, PSI will incorporate a powerful new modality for phase gradient imaging (PGI) in the inner retina. CAORI originally emphasized line-confocal imaging of photoreceptors in the outer retina in the bright-field reflectance mode. However, in recent years, following the groundbreaking work of AOSLO researchers, so-called ?dark-field? and split-detection AOSLO modalities with various combinations of offset detection apertures allow very subtle phase objects to be indirectly imaged in relatively transparent retinal layers, including microvasculature and neural somas (cell bodies of retinal ganglion cells, for example). Such features can used for early identification of new biomarkers in neurovascular and neurodegenerative conditions such as diabetic retinopathy and glaucoma. In Phase I, PSI has proven that CAORI can be adapted, within the same general line-confocal paradigm and footprint, for direct, sensitive, multi-aperture phase gradient imaging (PGI) in the inner retina. In particular, a time domain integration (TDI) line-camera enables line-confocality of the AO-LSO to be broadly adjusted, increasing collection aperture(s) without loss of image resolution (~2.4m) or light sensitivity. Simultaneous bright-field confocal ophthalmoscopy and a new type of oblique back- illuminated line ophthalmoscopy for directly imaging inner retinal layers in transmission was demonstrated on a single focal plane. Differencing pairs of inner retinal-focused TDI images (and videos) with complementary line offsets produces phase gradient images?the line-field AO-LSO equivalent of split-detection AOSLO. PSI will modify existing CAORI beta prototypes for PGI and begin clinical testing of these system in collaboration with researchers at New York Eye and Ear Infirmary, Mount Sinai (diabetic retinopathy), and NYU Langone Medical Center (glaucoma).